Dan: Following on my comment above, here is my attempt to articulate how I see things.
You are a man, and I am a man. That is our sexual identity. With respect to sexual identity, I consider us the same.
We are also fallen men; that is, we are heirs of original sin, and of the consequences of original sin called concupiscience. Among these consequences, we are subject to disordered appetites. Rightly ordered appetites are properly and temperately ordered toward their true objects. Disordered appetites are inflamed, excessive, demanding, and/or directed toward improper objects.
Behind this language of proper vs. improper objects is a teleological thesis, a thesis that embraces and presupposes order and design. The eye is ordered toward seeing. An eye capable of seeing is sound; an eye incapable of seeing is unsound.
Appetites also have teleology. Hunger is ordered toward nourishing the body. Hunger for food with nourishment in it is rightly ordered hunger; hunger for things that are not food at all—desire to eat hair, for example, or clay, or pencil shavings—is disordered appetite (a type of eating disorder called pica or allotriophagy).
In Christian anthropology, the teleology of the sexual powers and of sexual desire is considered especially serious. That’s because the exercise of sexual function is connected with—indeed, ordered toward—the procreation of new life. Even on a natural level, this is formidably grave because engendering new life is such a momentous thing, calling for the most serious commitment from both spouses. On a spiritual level, it’s even more serious because a new life is also a new immortal soul.
Beyond even this, divine revelation calls us to see sexual behavior as a matter of still greater gravity. God’s Word teaches us that the union of man and woman has a finality and definitiveness that we express in the mysterious phrase “one flesh.” St. Paul tells us that even in debased forms, sexual behavior still bumps up against this reality: Even a man united to a harlot becomes one flesh with her.
If all this weren’t enough, there is also a mysterious connection or correspondence between sexual union and the relationship of God to His people, both Israel and new Israel, the Church. There is a sacred or sacramental teleology in which the mutual self-giving of husband and wife, sharing themselves with one another without reservation, holding nothing back, mirrors or makes visible the union of God and His people. The fecundity of a fruitful marriage mirrors the spiritual fruitfulness of the soul united to God. It even mirrors the live-giving love of the Holy Trinity itself, in which the mutual self-giving of the First and Second Persons of the Blessed Trinity is the cause of the procession of the Third Person. Likewise, the ecstasy of sexual union represents the joy of heaven and ultimately the joy of the Trinity.
In view of all this, in the Christian order, marriage is elevated to a sacrament and held to be absolutely indissoluble. We truck here not only in the realm of morality and ethics, but in the realm of the sacred. A man who commits adultery, or who leaves his wife for another woman, is guilty not only of infidelity but of in effect lying about God, of enacting God’s abandonment of His people.
In view of all of the above, Christian morality, guided—so we believe as Catholics—by the Holy Spirit, has always seen sexual morality in the most exacting of terms. It is hard because our appetites are disordered, but it is demanding because the stakes are so high.
Any use of our sexual powers, from the deliberate stimulation of erotic desire and arousal to deliberate climax, is by definition is an exercise of the reproductive powers. Our capacity for arousal and climax is ordered toward procreation; that teleology must be respected in any exercise of the reproductive powers.
The wholesome and rightly ordered pursuit of erotic pleasure must be in keeping with the reality of being called one flesh, between partners who are joined for life and who share with one another their reproductive powers without holding anything back. Beyond this, only sexual union that mirrors the union of the Trinity and of God and His people—union of complementaries, union of the sort that completes the duality of human nature as male and female.
This doesn’t mean that pleasure, intimacy, and the expression of love are in any way invalid motives for marital union; nor does it mean that sex must always aim for procreation, or that sex during infertile periods is somehow unworthy. It does mean that marital union must always be pursued in a way that is in keeping with the teleology of the act. Whenever a couple enact the mystery of one flesh, it is always an act of giving themselves to one another wholly and without reservation, in the fullness of their reproductive powers at that moment. (In the same way, we can eat not only to nourish the body, but also because it tastes good, for social reasons, etc., but we must always eat in a manner in keeping with the fact that eating is for nutrition and digestion. Eating for social reasons does not justify purging; nor does sex for fun justify contraception.)
We can boldly pursue this line of thought in microscopic detail, without fear of Pythonesque jibes at our expense. The teleology of the male climax is to release seed to swim madly about in the female reproductive tract searching for an egg to fertilize—an egg that the vast majority of them will of course fail to join, and which probably isn’t there in any case, but it is still their teleology to search for it, and they can only do it there. There is no other tract in the body, male or female, in which seed can fulfill their teleology.
You call yourself gay; that is, so it seems to me, you self-identify with what Christianity teaches is a disordering of your appetites. I also have disorderings of my appetites, different from yours, but I don’t self-identify with them. I am a man, and you are a man. That is the fundamental reality, rooted in the order of creation: male and female He created them.
You are attracted to men. There is something disordered in this, although behind or beyond the disordering there is also something natural and good. What you perceive as attractive in masculinity is real and good, and it is right to appreciate and enjoy it. But it is not rightly available to you for erotic delectation, either in imagination or in reality.
To seek to do so is to use your sexuality contrary to teleology, both of nature and of the spirit, thereby doing violence to your own nature, to your sexual identity as a man. It is to indulge the disorderings of your appetites and thereby to reinforce them, doing further harm to yourself with respect to your concupiscent deformities. (The same is true of my concupiscent deformities.) It is also to violate the mystical meaning of your sexuality, thereby harming yourself with respect to your ultimate vocation of eternal union with God.
Hope that helps.
P.S. Which part of “Please explain specifically why you consider Scott’s term ‘evil’ not to be warranted by ‘grave depravity,’ or ‘causing harm’ by ‘contrary to natural law’” is confusing to you? NO, I don’t want you to explain IN GENERAL “why different words and groups of words can have different meanings from each other”; I want you to explain SPECIFICALLY why you consider THESE PARTICULAR PHRASES to be so disparate that the Catechism’s phrases don’t warrant Scott’s terms. I am totally serious and after I wrote out the above for you, you can jolly well oblige me. The nimbleness with which you continue to evade coming to grips with the question is impressive, but, well, so frigging what. For the fourth time, answer the damn question.